A device to device proximity service (D2D ProSe) between user equipment (UE) has become a hot topic for a Long Term Evolution (LTE) system.
Currently, in the D2D ProSe, to ensure that a receive end can correctly receive a signal sent by a transmit end, a timing advance needs to be provided when the transmit end sends the signal. An existing timing advance is usually an integral multiple (for example, 1, 2 or N, and N is a positive integer that is not less than 2) of a length of an extended cyclic prefix. Assuming that a used timing advance is a length of one extended cyclic prefix (for example, 6 bits), these 6 bits are all zeros, which may cause unnecessary waste.